The present invention relates to control mechanisms and pertains particularly to a steering rate sensing device for use in rotating air frames.
Many missiles have been designed for intentionally induced and maintained roll rates about their longitudinal axes during flight. Such missiles have significant and practical advantages over roll stabilized air frames. This rolling air frame concept has been applied to both air and surface launched missiles. These missiles can be spun up initially by the launcher and utilize control surfaces to maintain a predetermined rate of roll. With a roll rate of approximately 5 to 15 revolutions per second, it is possible to utilize a single control plane to guide the missile in all three earth related axes.
In a typical application of this concept, as disclosed in U.S. Pat. No. 4,037,806, the control system utilizes a single pair of variable incidence control surfaces to steer the missile about the control plane at a selected instantaneous rotational orientation upon command from a guidance command signal. Thus with such a missile operating in a level flight attitude, to cause the missile to climb, a guidance command signal must vary in amplitude at a frequency equal to the roll rate of the missile. For example, in the vertical plane, the guidance command signal would be generally sinusoidal wave form that would induce pitch-up as the control plane of the vehicle approaches earth vertical and pitch-down after the control surface rotates and nearest a one half revolution from pitch-up, thereby producing upward change in angle of attack. The angle of attack produces a body lift and alters the missile course from a horizontal to a climbing course. Similarly, a course change to the right would be effected by a sinusoidal signal displaced 90.degree. from the signal required for a vertical course change. This provides a simplified control system resulting in a reduction in cost and increase in reliability for rolling air frames as opposed to stabilized air frames.
The present invention was conceived and developed for utilization in a recently developed autopilot control system for rolling air frames. Such autopilot is disclosed in application Ser. No. 637,565, filed Dec. 4, 1975, by Donald R. Cole, entitled "Rolling Air Frame Autopilot", now U.S. Pat. No. 4,008,00, and assigned to the assignee hereof. Heretofore no adequate control devices have been available for use in such autopilot systems for rolling air frame systems.
It is therefore desirable that suitable steering rate sensing devices be available which are simple and effective for use in autopilot systems for rolling air frames.